DISCLAIMER; This is a working document provided by the Centers for Disease Control and Prevention (CDC) 

technical support contractor, SC&A, for use in discussions with the National Institute for Occupational Safety and 

Health (NIOSH) and the Advisory Board on Radiation and Worker Health (ABRWH), including its Working Groups 

or Subcommittees. Documents produced by SC&A, such as memorandum, white paper, draft or working documents 

are not final NIOSH or ABRWH products or positions, unless specifically marked as such. This document prepared 

by SC&A represents its preliminary evaluation on technical issues.

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 USC §552a and has been cleared for distribution. 

MEMORANDUM

TO: Fernald Work Group 

FROM: SC&A, Inc.

DATE: June 13, 2018 

SUBJECT: SC&A Analysis of Recycled Uranium Constituents at Fernald (1961–1972) 

Background 

The subject of appropriately bounding ratios of the main contaminants in recycled uranium

(RU)—plutonium (Pu), neptunium (Np), and technetium (Tc)—at Fernald have been the subject 

of substantial and extensive discussions between the Work Group, the National Institute for

Occupational Safety and Health (NIOSH), and SC&A for many years and numerous Work

Group meetings. The most recent discussions occurred during the two prior Work Group 

teleconference meetings held on July 28, 2017, and March 15, 2018 (ABRWH 2017, 2018). 

During the July 2017 meeting, SC&A expressed concern that the assumed contaminant ratios 

present in the updated Fernald site profile technical basis document for occupational internal 

dose (NIOSH 2017a) for the period from 1961 to 1972 did not comport with the contaminant 

ratios previously agreed upon by the Work Group, NIOSH, and SC&A.1

1 The ratios were discussed and agreed upon during the February 2012 Work Group meeting (see ABRWH 2012, 

pages 157–178).

 In response, NIOSH 

indicated that the available data had been reexamined and the ratios prior to 1973 were actually 

much lower than what had been described in NIOSH 2011. In particular, the ratio of plutonium 

to uranium at the site were all likely less than 10 parts per billion (ppb) (a factor of 10 lower than 

the previously agreed-upon ratio of 100 ppb). 

Subsequent to this meeting, NIOSH provided Revision 5 of the Issues Resolution Matrix for 

Fernald Site Profile and SEC Petition (NIOSH 2017b), which stated the position on RU

constituents as based on the available RU data found in U.S. Department of Energy (DOE) 2000: 

NIOSH’s use of the 10 ppb Pu in RU through 1972 is based on the lot data found 

in Attachment C of the Ohio Field Office Report [DOE 2000]. From a quick 

review of the lots identified as being processed prior to 1973, it appears that more 

than 95% of the identified Pu concentrations are below 1 ppb. Of those that are 

above 1 ppb Pu, most of those are still below 10 ppb Pu. This means that any 

potential to exposures to RU with Pu concentrations great than 10 ppb would be 

considered rare and to be short in duration. The remaining and thus majority of 

any worker’s exposure time would have been associated with materials well 

below the recommended default level of 10 ppb Pu. Therefore, NIOSH cannot 

 
Memo – Analysis of RU Constituents at Fernald 2 SC&A – June 13, 2018

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 USC §552a and has been cleared for distribution. 

identify any reason to believe that any worker could have an exposure for which 

the recommended default level of 10 ppb Pu would not be adequately conservative 

and bounding. [pages 3–4] 

During the March 2018 Fernald Work Group meeting, SC&A presented a preliminary analysis of 

the DOE 2000 data that did not agree with the NIOSH conclusion that 95% of the data were

below 1 ppb (ABRWH 2018). Because the SC&A analysis was preliminary and informal at that 

time, the Work Group tasked SC&A with formalizing their analysis for further consideration. 

This memorandum presents SC&A’s formal presentation of the analysis of RU data found in 

DOE 2000 for the period of interest (1961–1972). 

Analysis of Recycled Contaminant Database 

As stated in the previous section, analytical data characterizing the relative constituent levels in 

RU are provided in DOE 2000. The DOE report provides a significant amount of data, which 

extend beyond the period of interest for this analysis (19612

–1972). However, NIOSH noted that 

the DOE report provides methods for interpreting the “Lot ID” of each data measurement to 

determine the date of the measurement. SC&A used this identification method to restrict its 

analysis to only recycled constituent measurements taken prior to 1973. 

2 Although the period of interest begins in 1961, the data in DOE 2000 do not begin until 1962.

Table 1 shows the available constituent data for this period after they were fit to a lognormal 

distribution. As seen in the table, the lognormal geometric mean for plutonium is much less than 

NIOSH’s assumed default value of 10 ppb and also less than 1 ppb. However, the associated 

geometric standard deviation associated with the lognormal fit is quite large (24.18) and results 

in a 95th-percentile contaminant ratio that is over a factor of 12 higher than the NIOSH default

for plutonium contamination in RU. As was noted by NIOSH during the March 2018 Work 

Group meeting, the very high geometric standard deviation (and associated 95th-percentile 

value) is likely indicative of multiple distributions present in the dataset (see pages 22–23 of 

ABRWH 2018). Therefore, fitting all of the data to a single lognormal distribution may not be 

appropriate. 

Table 1. Overview of Recycled Uranium Constituent Data Fit to a Lognormal Distribution 

(1962–1972) 

Parameter Plutonium (ppb) Neptunium (ppb) Technetium (ppb)

Lognormal geometric 

mean (ppb) 0.656 319.20 60.88 

Lognormal geometric 

standard deviation 24.18 3.57 26.16 

Lognormal 95th percentile 

(ppb) 124.14 2,592.60 13,074.98 

As such, SC&A opted for a more simplistic analytical approach, as shown in Table 2. As seen in 

the table, the revised analysis includes traditional metrics, such as the arithmetic average, 

 
Memo – Analysis of RU Constituents at Fernald 3 SC&A – June 13, 2018

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 USC §552a and has been cleared for distribution. 

arithmetic median, and rank-ordered 95th percentile. A simple rank ordering of the available 

plutonium data is also displayed in Figure 1. As seen in the table and figure, the 95th-percentile 

rank-ordered plutonium concentration is nearly 4 times the NIOSH-recommended default of 

10 ppb. In addition, nearly 22% of the observed plutonium constituent data are above the 10 ppb 

recommended default value. 

Table 2. Overview of Recycled Uranium Constituent Data by Traditional Metrics 

(1962–1972) 

Parameter Plutonium

Data Neptunium Data Technetium Data

Arithmetic average (ppb) 15.21 1,383.85 3,283.99

Arithmetic median (ppb) 2.01 346.57 23.00

Rank-ordered 95th

percentile (ppb) 38.71 1,862.97 11,950 

Maximum observed 

sample (ppb) 1,305 75,837.84 207,619.2 

Number of samples 

below NIOSH default 

values (%)

491 (78.2%) 223 (54.8%) 293 (83.5%) 

Number of samples 

above NIOSH default 

values (%)

137 (21.8%) 184 (45.2%) 58 (16.5%) 

Figure 1. Rank Order of Plutonium Contaminant Concentrations in Recycled Uranium 

(1962–1972) 
Memo – Analysis of RU Constituents at Fernald 4 SC&A – June 13, 2018

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 USC §552a and has been cleared for distribution. 

SC&A also analyzed the data by the process subgroups developed in DOE 2000 (see Table 3). 

Analyzed constituent values are italicized in red in Table 3 if they are higher than the NIOSHproposed default values. As seen in Table 3, the average plutonium constituent concentrations 

for DOE 2000 Subgroups 9, 10A, 10B, and 11 were all greater than the NIOSH default for 

plutonium and neptunium. 

Table 3. Overview of Average RU Constituent Data by Subgroup, 1962–1972 

(entries shown in red italics exceed the NIOSH-proposed defaults of 10 Pu ppb, 

400 Np ppb, and 6,000 Tc ppb)

DOE 

2000 

Subgroup

# Pu 

Results

Arithmetic 

Average Pu 

(ppb)

# Np 

Results

Arithmetic 

Average Np 

(ppb)

# Tc 

Results

Arithmetic 

Average Tc 

(ppb)

1A 1 2.22 No Data No Data No Data No Data

1B 39 0.92 39 107.58 2 0.55

2 1 0.13 1 15.95 No Data No Data

3 No Data No Data No Data No Data No Data No data

4 199 0.06 1 58.77 195 9.71

5 No Data No Data No Data No Data No Data No data

6A 21 2.32 21 401.04 21 9,118.10

6B 34 1.78 34 452.15 34 10,801.76

6C 122 6.46 105 1,092.26 84 6,823.87

6D No Data No Data No Data No Data No Data No data

6E No Data No Data No Data No Data No Data No data

6F No Data No Data No Data No Data No Data No data

7A No Data No Data No Data No Data No Data No data

7B 1 1.38 1 344.52 1 2,279.00

8 No Data No Data No Data No Data No Data No Data

9 25 55.20 24 3825.81 1 367.42

10A 20 159.58 20 10,249.23 No Data No Data

10B 134 21.86 134 519.18 No Data No Data

11 31 35.59* 27 1,990.99 13 1,245.76

Total 628 15.21 407 1,383.85 351 3,283.99

*Note that this result is dominated by a single 1962 result of 942.5 ppb Pu described in the database as an “Oliver 

Filter” and also “Discard Process Residues, Trailer Cakes, Waste Slurries, Raffinates, Etc.” If this value is 

removed, the average drops to 5.36 ppb for Subgroup 11.

Finally, SC&A analyzed the data by year for the period of interest (see Table 4). Similar to the 

previous table, analyzed constituent values are italicized in red in Table 4 if they are higher than 

the NIOSH proposed default values. As seen in Table 4, the average plutonium constituent 

concentrations generally increased over time, with calculated average values above the NIOSH 

default values from 1969 to 1972. For neptunium, 9 of the 11 years analyzed showed average 

values above the recommended default. 
Memo – Analysis of RU Constituents at Fernald 5 SC&A – June 13, 2018

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 USC §552a and has been cleared for distribution. 

Table 4. Overview of Average RU Constituent Data by Year, 1962–1972 

(entries shown in red italics exceed the NIOSH-proposed defaults of 10 Pu ppb, 

400 Np ppb, and 6,000 Tc ppb)

Subgroup # Pu 

Results

Average Pu 

(ppb)

# Np 

Results

Average Np 

(ppb)

# Tc 

Results

Average Tc 

(ppb)

1962 174 6.99 66 511.82 143 1,356.97

1963 63 3.35 43 285.13 41 3,394.20

1964 59 5.31 44 461.71 47 2,725.59

1965 26 6.81 23 509.51 11 2,823.79

1966 36 7.97 21 422.34 12 249.59

1967 61 7.47 47 319.23 18 2,500.58

1968 53 9.47 22 3,847.00 28 3,603.84

1969 36 20.01 29 1,446.76 14 2,208.91

1970 34 23.79 34 612.25 8 28,394.55

1971 34 79.84 34 4,863.72 13 16,678.72

1972 52 41.27 44 3,375.18 16 2,280.59

Total 628 15.21 407 1,383.85 351 3,283.99

Summary Conclusion 

Based on its review of the available constituent data provided in DOE 2000 and described above, 

SC&A does not feel that sufficient analytical evidence has been developed and discussed to 

justify the lower ratios of RU constituents as provided in NIOSH 2017a. SC&A does not agree 

with the rationale provided in NIOSH 2017b that 95% of the available constituent data for 

plutonium are less than 1 ppb and thus sufficiently bounded by an assumed default value of 

10 ppb. It is recommended that NIOSH revisit its assumed default values to assure that assigned 

doses are sufficiently claimant favorable and bounding for all potentially exposed workers. 

References

ABRWH 2012. Transcript: Meeting of the Advisory Board on Radiation and Worker Health, 

Fernald Work Group, Hebron, KY. February 9, 2012. 

ABRWH 2017. Transcript: Teleconference Meeting of the Advisory Board on Radiation and 

Worker Health, Fernald Work Group. July 28, 2017. 

ABRWH 2018. Transcript: Teleconference Meeting of the Advisory Board on Radiation and 

Worker Health, Fernald Work Group. March 15, 2018 

DOE 2000. Recycled Uranium Project Report, DOE 00-0001, U.S. Department of Energy, Ohio 

Field Office. May 15, 2000. [SRDB Ref. ID 3644] 

NIOSH 2011. Issues Related to the Ability to Bound Internal Dose from Recycled Uranium 

Trace Level Contaminants at Fernald, Draft 01, National Institute for Occupational Safety and 

Health, Cincinnati, OH. August 5, 2011. 
Memo – Analysis of RU Constituents at Fernald 6 SC&A – June 13, 2018

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 USC §552a and has been cleared for distribution.

NIOSH 2017a. Feed Materials Production Center – Occupational Internal Dose, ORAUTTKBS-0017-5, Revision 03, National Institute for Occupational Safety and Health, Cincinnati, 

OH. March 30, 2017.

NIOSH 2017b. Issues Resolution Matrix for Fernald Site Profile and SEC Petition, Revision 5, 

National Institute for Occupational Safety and Health, Cincinnati, OH. October 24, 2017.